Super-elastic titanium alloy for living body

ABSTRACT

Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; at least one element selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd) and silver (Ag): Au: from over 0 to 10 mol %, Pt: from over 0 to 10 mol %, Pd: from over 0 to 10 mol %, Ag: from over 0 to 10 mol %, wherein a total thereof being up to 20 mol %; and balance being titanium and inevitable impurities.

FIELD OF THE INVENTION

The present invention relates to a super-elastic titanium alloy for a living body, in particular a titanium alloy of Ti—Nb—Au, Ti—Nb—Pt, Ti—Nb—Pd, and Ti—Nb—Ag having excellent super elasticity which is suitably applicable to medical equipments.

RELATED ART

Recently, an alloy material having super elasticity is used in a medical field. For example, a Ti—Ni alloy has excellent strength, antifriction property and corrosion resistance, and furthermore conformability to a living body, thus applied as material for a living boy to various medical equipments.

However, the material for a living body using Ti—Ni alloy may cause allergosis due to Ni composition contained therein. There are proposed a Ti—Nb—Sn shape-memory alloy for a living body (in Japanese Patent Provisional Publication 2001-329325) and a Ti—Mo—Ga—Al—Ge alloy having super elasticity for a living body (in Japanese Patent Provisional Publication 2003-293058), each of which does not contain any component having toxicant or to cause allergosis including Ni, thus being more safer material for a living body.

Since the titanium alloy not containing Ni as proposed in Japanese Patent Provisional Publication 2001-329325 and Japanese Patent Provisional Publication 2003-293058 becomes available, a development of a product effectively using super-elasticity or shape-memory property is encouraged in a field in which the product is inserted in the living body or is directly contacted with bare skin.

However, when the above-mentioned titanium alloy not containing Ni is applied to various medical appliances such as a medical guide wire, orthodontic wire, stent, and further a daily product which is directly contacted with bare skin such as a frame for an eyeglasses or a nose pad for an eyeglasses, the cold workablity or super elasticity thereof is not satisfactory, thus it is expected to develop a material having a higher level of performance.

SUMMARY OF THE INVENTION

One of the object of the present invention is to provide a super-elastic titanium alloy without containing Ni, and having an excellent super elasticity and cold workablity as well as excellent productivity.

The first embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase:         -   from 5 to 40 mol %;     -   at least one element selected from the group consisting of gold         (Au), platinum (Pt), palladium (Pd) and silver (Ag):         -   Au: from over 0 to 10 mol %,         -   Pt: from over 0 to 10 mol %,         -   Pd: from over 0 to 10 mol %,         -   Ag: from over 0 to 10 mol %,             -   wherein a total thereof being up to 20 mol %; and     -   balance being titanium and inevitable impurities.

In the first embodiment of the super-elastic titanium alloy for a living body, Au: from over 0 to 5 mol %, Pt: from over 0 to 5 mol %, Pd: from over 0 to 5 mol %, Ag: from over 0 to 5 mol %, wherein a total thereof being up to 10 mol %.

The third embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   gold (Au): from over 0 to 10 mol %, and balance being titanium         and inevitable impurities.

The fourth embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   platinum (Pt): from over 0 to 10 mol %, and     -   balance being titanium and inevitable impurities.

The fifth embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   palladium (Pd): from over 0 to 10 mol %, and     -   balance being titanium and inevitable impurities.

The sixth embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   silver (Ag): from over 0 to 10 mol %, and     -   balance being titanium and inevitable impurities.

The seventh embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   gold (Au): from over 0 to 10 mol %;     -   platinum (Pt): from over 0 to 10 mol %;     -   palladium (Pd): from over 0 to 10 mol %; and     -   balance being titanium and inevitable impurities.

The eighth embodiment of the super-elastic titanium alloy for a living body consisting essentially of:

-   -   Niobium (Nb) as an element to stabilize β-phase: from 5 to 40         mol %;     -   gold (Au): from over 0 to 10 mol %;     -   platinum (Pt): from over 0 to 10 mol %; and     -   balance being titanium and inevitable impurities.

A medical guide wire of the invention comprises one which uses the super-elastic titanium alloy for a living body as described in the above.

A orthodontic wire of the invention comprises one which uses the super-elastic titanium alloy for a living body as described above.

A stent of the invention comprises one which uses the super-elastic titanium alloy for a living body as described above.

An endoscope actuator of the invention comprises one which uses the super-elastic titanium alloy for a living body as described above.

Material for eyeglasses of the invention comprises one which uses the super-elastic titanium alloy for a living body as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a typical example of a schematic cross sectional view of the heater plate of one embodiment of the invention;

FIG. 2 is a schematic plan view of the heater plate of the invention;

DETAILED DESCRIPTON OF THE INVENITION

In the alloy of the present invention, Nb is a component having a function to stabilize β-phase. Ti—Nb alloy prepared by adding Nb is to Ti becomes the alloy in which a thermoelastic Martensitic transformation is to be produced. Furthermore, Nb has a function to cause a transformation temperature from β-phase to α-phase to lower to a lower temperature side. This means that an alloy in which the β-phase as a substrate phase in the Martensitic transformation is stable at room temperature can be obtained.

An amount of Nb contained in the alloy is limited to be within a range of from 5 mol % to 40 mol %. With less than 5 mol % of Nb, or with more than 40 mol % of Nb, super elasticity of the alloy is not realized, or is lowered.

One or more than two compositions selected from the group consisting of Au, Pt, Pd, and Ag is contained in the alloy, while a total of the amount of the above-mentioned selected compositions is up to 20 mol %. With the total amount of up to 20 mol % of the above-mentioned selected compositions, a more excellent super elasticity can be obtained. With the total amount of over 20 mol % of the above-mentioned selected compositions, on the contrary, the workablity thereof is remarkably lowered. Each of the above-mentioned Au, Pt, Pd, and Ag may be contained in the alloy from over 0 to 10 mol %. More specifically, Au: from over 0 to 10 mol %, Pt: from over 0 to 10 mol %, Pd: from over 0 to 10 mol %, Ag: from over 0 to 10 mol %. With from over 0 to 10 mol % of each of Au, Pt, Pd, and Ag (one or more than two those compositions are selected and the total amount thereof is up to 20 mol %), Ti₃Au, Ti₃Pt, Ti₄Pd and/or Ti₂Ag are precipitated in the eutectoid reaction in a heat treatment, thus improving super elasticity of the alloy. Furthermore, fine structure is produced by the eutectoid reaction to obtain stable super elasticity in the alloy. With from over 0 to 10 mol % of at least one of Au, Pt, Pd, and Ag (even though one or more than two those compositions are selected and the total amount thereof is up to 20 mol %), the super elasticity is lowered, and the cold workability is remarkably lowered so that it is not possible to work. Each of the above-mentioned compositions has conformability to a living body, and has a higher radiopaque contrast effect.

In case that a higher cold workablity is expected in the alloy, each of the above-mentioned Au, Pt, Pd, and Ag may be contained in the alloy from over 0 to 5 mol % (i.e., Au: from over 0 to 5 mol %, Pt: from over 0 to 5 mol %, Pd: from over 0 to 5 mol %, Ag: from over 0 to 5 mol %), while one or more than two those compositions are selected and the total amount thereof is up to 10 mol %.

Since the Ti—Nb—X (X=at least one of Au, Pt, Pd, and Ag) alloy of the present invention has excellent super elasticity as the super-elastic titanium alloy for a living body, and has excellent conformability to a living body without causing allergosis, the alloy is applicable to a medical equipment for a living body such as a medical guide wire, orthodontic wire, stent, or actuator for an endoscope. Furthermore, the alloy can be applied to the product directly contacting with the bare skin such as a frame for an eyeglasses or a nose pad for an eyeglasses.

The present invention is described in more detail by the examples.

EXAMPLES Example 1

A Ti—Nb—Au alloy ingot having the alloy composition as shown in Table 1 is prepared in the non-consumable tungsten electrode type argon arc smelting furnace. Hot working is applied to thus prepared alloy ingot, then, the process annealing of retaining for 10 minutes at the temperature of 700 degree centigrade and the cold wire drawing are repetitively applied thereto, and then, the finishing cold wire drawing at 40% of finishing cold working rate is applied thereto to prepare cold working materials having a wire diameter of 1.0 mm respectively as samples. A linear shape-memory heat treatment for 2 minutes at the temperature of 800 degree centigrade is applied to the part of the samples (the cold working material) to prepare samples (a shape-memory material). The finishing cold wire drawing at 20% finishing cold working rate is applied to the wire materials which are not wire-drawn at the 40% finishing cold working rate.

The super elasticity is evaluated on the samples (the shape-memory material), and the cold workability is evaluated on the samples (the cold working material), and the results thereof are shown in Table 1.

More specifically, the super elasticity is evaluated as follows: The samples (the shape-memory material) are held at the temperature of 37 degree centigrade in the constant temperature bath, then the respective samples are wound one time around the stainless steel round bar having a diameter of 10 mm so as to be bent 180 degrees and retained for 30 seconds as thus bent. Then, the retention is removed from the samples (the shape-memory material) and the extent of returning to the original linear shape of the samples are investigated to evaluate the super elasticity. The extent of returning to the original linear shape is investigated by measuring a bent angle from the original linear shape.

FIG. 1 shows a method for measuring the bent angle from the linear shape. The reference numeral 1 indicates the sample (the shape-memory material), and the reference numeral 2 indicates the stainless steel round bar. As shown in FIG. 1, the sample (the shape-memory material) 1 is wound one time around the stainless steel round bar 2 so as to be bent 180 degrees and retained for 30 seconds as thus bent, and then the retention is removed from the sample. The angle 0 in FIG. 1 shows the extent of returning to the original linear shape of the sample in connection to the horizontal plane. In case that the angle θ is up to 5 degrees, super elasticity is evaluated to be excellent and shown as ◯, and in case that the angle θ is over 5 degrees, super elasticity is evaluated to be bad and shown as Δ.

The cold workability is evaluated as follows: The sample (the cold working material) is annealed for 10 minutes at the temperature of 700 degree centigrade to prepare an annealed material. The cold wire drawing is applied to thus prepared annealed material until the annealed material is broken. The maximum wire drawing rate in which the annealed material is broken is investigated. The cold workability is evaluated by the maximum wire drawing rate. In case that the maximum wire drawing rate is over 40%, the cold workability is evaluated to be excellent and shown as ◯, in case that the maximum wire drawing rate is between a range of from over 20% to below 40%, the cold workability is evaluated to be a little inferior and shown as Δ, and in case that the maximum wire drawing rate is up to 20%, the cold workability is evaluated to be poor and shown as x. TABLE 1 Sample Composition (mol %) Super Cold No. Nb Au Ti elasticity workability Samples 1 5.0 3.0 balance ◯ ◯ of 2 5.0 5.0 balance ◯ ◯ the 3 5.0 10.0 balance ◯ Δ present 4 20.0 3.0 balance ◯ ◯ invention 5 20.0 5.0 balance ◯ ◯ 6 20.0 10.0 balance ◯ Δ 7 40.0 3.0 balance ◯ ◯ 8 40.0 5.0 balance ◯ ◯ 9 40.0 10.0 balance ◯ Δ Comparative 100 20.0 15.0 balance X Δ samples 101 — 3.0 balance X ◯ 102 50.0 3.0 balance X ◯

As is clear from Table 1, each of the samples Nos. 1 to 9 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 1, 2, 4, 5, 7 and 8 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 100, which contains Au over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 101, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 102, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. Furthermore, the comparative sample No. 100 has deteriorate cold workability, in addition to the above defect property.

Example 2

Samples of a Ti—Nb—Pt alloy having the alloy composition as shown in Table 2 are prepared in the same manner as in Example 1. The super elasticity and the cold workability are evaluated on the samples in the same manner as in Example 1, and the results thereof are shown in Table 2. TABLE 2 Sample Composition (mol %) Super Cold No. Nb Pt Ti elasticity workability Samples 10 5.0 3.0 balance ◯ ◯ of 11 5.0 5.0 balance ◯ ◯ the 12 5.0 10.0 balance ◯ Δ present 13 20.0 3.0 balance ◯ ◯ invention 14 20.0 5.0 balance ◯ ◯ 15 20.0 10.0 balance ◯ Δ 16 40.0 3.0 balance ◯ ◯ 17 40.0 5.0 balance ◯ ◯ 18 40.0 10.0 balance ◯ Δ Comparative 103 20.0 15.0 balance X Δ samples 104 — 3.0 balance X ◯ 105 50.0 3.0 balance X ◯

As is clear from Table 2, each of the samples Nos. 10 to 18 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 10, 11, 13, 14, 16 and 17 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 103, which contains Pt over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 104, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 104, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. Furthermore, the comparative sample No. 103 has deteriorate cold workability, in addition to the above defect property.

Example 3

Samples of a Ti—Nb—Pd alloy having the alloy composition as shown in Table 3 are prepared in the same manner as in Example 1. The super elasticity and the cold workability are evaluated on the samples in the same manner as in Example 1, and the results thereof are shown in Table 3. TABLE 3 Sample Composition (mol %) Super Cold No. Nb Pd Ti elasticity workability Samples 19 5.0 3.0 balance ◯ ◯ of 20 5.0 5.0 balance ◯ ◯ the 21 5.0 10.0 balance ◯ Δ present 22 20.0 3.0 balance ◯ ◯ invention 23 20.0 5.0 balance ◯ ◯ 24 20.0 10.0 balance ◯ Δ 25 40.0 3.0 balance ◯ ◯ 26 40.0 5.0 balance ◯ ◯ 27 40.0 10.0 balance ◯ Δ Comparative 106 20.0 15.0 balance X Δ samples 107 — 3.0 balance X ◯ 108 50.0 3.0 balance X ◯

As is clear from Table 3, each of the samples Nos. 19 to 27 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 19, 20, 22, 23, 25 and 26 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 106, which contains Pd over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 107, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 108, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. Furthermore, the comparative sample No. 106 has deteriorate cold workability, in addition to the above defect property.

Example 4

Samples of a Ti—Nb—Ag alloy having the alloy composition as shown in Table 4 are prepared in the same manner as in Example 1. The super elasticity and the cold workability are evaluated on the samples in the same manner as in Example 1, and the results thereof are shown in Table 4. TABLE 4 Sample Composition (mol %) Super Cold No. Nb Ag Ti elasticity workability Samples 28 5.0 3.0 balance ◯ ◯ of 29 5.0 5.0 balance ◯ ◯ the 30 5.0 10.0 balance ◯ Δ present 31 20.0 3.0 balance ◯ ◯ invention 32 20.0 5.0 balance ◯ ◯ 33 20.0 10.0 balance ◯ Δ 34 40.0 3.0 balance ◯ ◯ 35 40.0 5.0 balance ◯ ◯ 36 40.0 10.0 balance ◯ Δ Comparative 109 20.0 15.0 balance X Δ samples 110 — 3.0 balance X ◯ 111 50.0 3.0 balance X ◯

As is clear from Table 4, each of the samples Nos. 28 to 36 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 28, 29, 31, 32, 34 and 35 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 109, which contains Ag over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 110, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 111, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. Furthermore, the comparative sample No. 109 has deteriorate cold workability, in addition to the above defect property.

Samples of a Ti—Nb—Au—Pt alloy having the alloy composition as shown in Table 5 are prepared in the same manner as in Example 1. The super elasticity and the cold workability are evaluated on the samples in the same manner as in Example 1, and the results thereof are shown in Table 5. TABLE 5 Cold Sample Composition (mol %) Super worka- No. Nb Au Pt Ti elasticity bility Samples 37 5.0 3.0 3.0 balance ◯ ◯ of 38 5.0 5.0 5.0 balance ◯ ◯ the 39 5.0 10.0 10.0 balance ◯ Δ present 40 20.0 3.0 3.0 balance ◯ ◯ invention 41 20.0 5.0 5.0 balance ◯ ◯ 42 20.0 10.0 10.0 balance ◯ Δ 43 40.0 3.0 3.0 balance ◯ ◯ 44 40.0 5.0 5.0 balance ◯ ◯ 45 40.0 10.0 10.0 balance ◯ Δ Compar- 112 20.0 15.0 15.0 balance X Δ ative 113 — 3.0 3.0 balance X ◯ samples 113 50.0 3.0 3.0 balance X ◯

As is clear from Table 5, each of the samples Nos. 37 to 45 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 37, 38, 40, 41, 43 and 44 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 113, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 114, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 112, which contains both of Au and Pt respectively over the upper limit of 10 mol %, has so remarkably deteriorate cold workability that the sample (cold working material) having a wire diameter of 1.0 mm cannot be prepared, thus no evaluation is effected.

Example 6

Samples of a Ti—Nb—Au—Pt—Pd alloy having the alloy composition as shown in Table 6 re prepared in the same manner as in Example 1. The super elasticity and the cold workability are evaluated on the samples in the same manner as in Example 1, and the results thereof are shown in Table 6. TABLE 6 Sam- Super Cold ple Composition (mol %) elas- work- No. Nb Au Pt Pd Ti ticity ability Samples 46 5.0 3.0 3.0 3.0 balance ◯ ◯ of 47 5.0 7.0 7.0 6.0 balance ◯ Δ the 48 20.0 3.0 3.0 3.0 balance ◯ ◯ present 49 20.0 7.0 7.0 6.0 balance ◯ Δ invention 50 30.0 3.0 3.0 3.0 balance ◯ ◯ 51 30.0 7.0 7.0 6.0 balance ◯ Δ Compar- 115 20.0 10.0 10.0 10.0 balance — X ative 116 40.0 10.0 10.0 10.0 balance X Δ samples 117 — 3.0 3.0 3.0 balance X ◯ 118 50.0 3.0 3.0 3.0 balance X ◯

As is clear from Table 6, each of the samples Nos. 46 to 51 of the invention has excellent super elasticity and shows that the shape thereof is restored. Furthermore, each of the samples Nos. 46, 48 and 50 of the invention has excellent cold workability, in addition to the above super elasticity. On the contrary, the comparative sample No. 117, which does not contain Nb, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 118, which contains 50 mol % of Nb over the upper limit of 10 mol %, does not have excellent super elasticity so that the shape thereof is not restored. The comparative sample No. 116, which contains 40 mol % of Nb, 10 mol % of Au, 10 mol % of Pt, and 10 mol % of Pd (total of Au, Pt and Pd is over the upper limit of 20 mol %), has excellent cold workability, however, has no super elasticity. The comparative sample No. 115, which contains 20 mol % of Nb, 10 mol % of Au, 10 mol % of Pt, and 10 mol % of Pd (total of Au, Pt and Pd is over the upper limit of 20 mol % as in the same manner as the comparative sample No. 116), has so remarkably deteriorate cold workability that the sample (cold working material) having a wire diameter of 1.0 mm cannot be prepared, thus no evaluation is effected.

Example 7

A Ti-20 mol % Nb-3 mol % Au alloy ingot having the alloy is prepared in the non-consumable tungsten electrode type argon arc smelting furnace. Hot working is applied to thus prepared alloy ingot, then, the process annealing of retaining for 10 minutes at the temperature of 700 degree centigrade and the cold wire drawing are repetitively applied thereto, and then, the finishing cold wire drawing at 40% of finishing cold working rate is applied thereto to prepare a cold working material having a wire diameter of 0.5 mm. A linear shape-memory heat treatment for 2 minutes at the temperature of 800 degree centigrade is applied to thus prepared cold working material to prepare a wire material for a medical guide wire, a wire material for an orthodontic wire, and a wire material for a linear actuator. The respective super elasticity investigated by the same method as described in Example 1 are shown in Table 7. Furthermore, torque transferability of the wire material for a medical guide wire is investigated by the method as depicted in FIG. 2, and the result thereof is also shown in Table 7.

The torque transferability is represented by a correspondingly induced angle of other end portion of the wire material received in a pipe to the opposite end portion when a twist under a specific condition is applied to the opposite end portion of the wire material. More specifically, as shown in FIG. 2, a sample 1 of the wire material is received in a loop shaped polyethylene pipe 5 having an inner diameter of 3 mm, and outer diameter of 4 mm, the diameter of which loop is 127 mm. One end portion of the sample 1 is twisted 90 degrees around the axis of the sample, and the correspondingly induced angle of the other end portion around the axis is measured. In case that the correspondingly induced angle is over 85 degrees, the torque transferability is evaluated to be excellent and shown as ⊚. In case that the correspondingly induced angle is within a range of from 80 to 85 degrees, the torque transferability is evaluated to be good and shown as ◯. In case that the correspondingly induced angle is within a range of from 75 to 80 degrees, the torque transferability is evaluated to be a little inferior and shown as Δ. In case that the correspondingly induced angle is below 75 degrees, the torque transferability is evaluated to be bad and shown as x. In FIG. 2, the reference numeral 6 a is a rotary encoder at the driving side, the reference numeral 6 b is a rotary encoder at the follow-up side, and the reference numeral 7 is a driving portion.

Example 8

The wire material to which the linear shape-memory heat treatment is applied for a frame of eyeglasses having a wire-diameter of 2.0 mm is prepared by the same method as in FIG. 7. The super elasticity thereof is measured in the same manner as in Example 7, and the result thereof is also shown in Table 7. TABLE 7 Wire Torque Diameter Super trans- Products (mm) elasticity ferability Samples Wire material for 0.5 ◯ ⊚ of the medical guide wire present Wire material for 0.5 ◯ — invention orthodontic wire Wire material for linear 0.5 ◯ — actuator Frame for eyeglasses 2.0 ◯ —

As is clear from Table 7, the Ti alloy of the invention has both of sufficiently excellent super elasticity and cold workability for such as the medical guide wire, orthodontic wire, linear actuator, frame for eyeglasses, nose pad arm for eyeglasses to which excellent super elasticity is required.

Example 9

The medical guide wire, the orthodontic wire and the frame for eyeglasses are prepared by the respective medical guide wire material, the orthodontic wire material and the frame material for eyeglasses prepared according to Examples 7 and 8. Thus prepared medical guide wire, the orthodontic wire and the frame for eyeglasses can be so comfortably wore without problem as the conventional products

The Ti alloy of the present invention in which Nb, and at least one elements of Au, Pt, Pd, Ag are added to titanium is realized to have both of excellent super elasticity and cold workability. Since the elements of the alloy of the present invention comprise those having conformability to a living body, and furthermore do not contain Ni, the alloy of the invention is suitably applicable to the medical equipment for a living body and the products directly contacting with the bare skin such as a frame for an eyeglasses, thus remarkably industrially effective. 

1. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; at least one element selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd) and silver (Ag): Au: from over 0 to 10 mol %, Pt: from over 0 to 10 mol %, Pd: from over 0 to 10 mol %, Ag: from over 0 to 10 mol %, wherein a total thereof being up to 20 mol %; and balance being titanium and inevitable impurities.
 2. The titanium alloy as claimed in claim 1, wherein Au: from over 0 to 5 mol %, Pt: from over 0 to 5 mol %, Pd: from over 0 to 5 mol %, Ag: from over 0 to 5 mol %, wherein a total thereof being up to 10 mol %
 3. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; gold (Au): from over 0 to 10 mol %, and balance being titanium and inevitable impurities.
 4. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; platinum (Pt): from over 0 to 10 mol %, and balance being titanium and inevitable impurities.
 5. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; palladium (Pd): from over 0 to 10 mol %, and balance being titanium and inevitable impurities.
 6. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; silver (Ag): from over 0 to 10 mol %, and balance being titanium and inevitable impurities.
 7. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; gold (Au): from over 0 to 10 mol %; platinum (Pt): from over 0 to 10 mol %; palladium (Pd): from over 0 to 10 mol %; and balance being titanium and inevitable impurities.
 8. Super-elastic titanium alloy for a living body consisting essentially of: Niobium (Nb) as an element to stabilize β-phase: from 5 to 40 mol %; gold (Au): from over 0 to 10 mol %; platinum (Pt): from over 0 to 10 mol %; and balance being titanium and inevitable impurities.
 9. A medical guide wire which uses the super-elastic titanium alloy for a living body as claimed in any one of claims 1 to
 8. 10. A orthodontic wire which uses the super-elastic titanium alloy for a living body as claimed in any one of claims 1 to
 8. 11. A stent which uses the super-elastic titanium alloy for a living body as claimed in any one of claims 1 to
 8. 12. An endoscope actuator which uses the super-elastic titanium alloy for a living body as claimed in any one of claims 1 to
 8. 13. Material for eyeglasses which uses the super-elastic titanium alloy for a living body as claimed in any one of claims 1 to
 8. 